PURPOSE: To regulate the discharge speed and the refrigerant consumption freely by providing an angle adjusting mechanism for adjusting the angle of a louver blind to be cooled through cooling liquid from the outside of a vacuum container on a cryo-pump.

CONSTITUTION: Upon operation of a drive shaft 17 from the outside of a vacuum container 3 to move straight forwardly, a louver blind 14 will rotate around a cooling tube 15 through a pin joint 19 thus to adjust the angle QL. Here, a bellows 20 will expand/contract to maintain vacuum in the vacuum container. If the relation between the angle of louver blind and the movement of drive shaft is determined previously, the angle of louver blind can be held at random value by securing the drive shaft at predetermined position through a locknut 21.